[visionlist] Teller Acuity Cards

[Gislin Dagnelie]

Chris and Meindert,

I definitely agree with Meindert's objection to the cards he presents.

One thing that is critically important about any card that intends to assess 
visual acuity (high-spatial frequency resolution, if you will) through 
high-resolution texture filling a contour is that:
1) the average luminance inside the contour is equal to that outside  it, and 
2) the edges of the contour are filtered, preferably with a raised cosine of a 
spatial frequency equal to the fundamental of the texture inside the contour.

Unless Meindert's photographic rendition is grossly misrepresenting the actual 
hues and greyscale levels on the new cards, the cards do not meet the first 
requirement:  In all cases the average luminance inside the contour is lower 
than outside.

The cards definitely do not meet the second requirement: there is no filtering 
around the contour edges

So I have to agree with Meindert that there are serious problems with these 
cards.

Note, BTW, that the Teller cards do not use filtering around the outside of the 
contour either, but this may be less important because of the square contour of 
each pattern: black and white bars are equal in area.  Still this may lead to 
an overestimation of acuity compared to an unconstrained grating

So while I agree with Chris that there is room for valid alternatives to the 
Teller cards, the ones shown here do not appear to meet the minimum 
requirements for such an alternative.

But maybe I'm missing something?

Gislin
-- 
Gislin Dagnelie, Ph.D.
Associate Professor of Ophthalmology
JHU Lions Vision Research & Rehab Center
Johns Hopkins Hospital, Wilmer Woods 358
1800 Orleans St
Baltimore, MD 21287-0023    http://ultralowvisionlabjhu.net/
USA			        e-mail: gislin at jhu.edu


On 13 Feb 2020 at 13:24, Christopher Taylor <christopher.taylor at gmail.com> 
wrote:

Why do you believe this test has a fundamental error versus TAC testing? It
is a different test, no more, no less.

To play devil's advocate, one could claim that Teller Acuity Cards lack
ecological validity because they do not present contours and objects, which
are more important to the visual system during daily living than sinusoidal
or square-wave gratings.  That said performance on this test and TAC ought
to correlate and if this new test has other benefits (e.g, faster/easier to
administer, cheaper and more available to purchase, and so on...) and has
appropriate age-norms for the population being screened then might it not
be an advance on traditional TAC testing?

Best,

C

On Thu, Feb 13, 2020 at 9:36 AM Meindert de Vries <meindertdevries at visio.org>
wrote:

> Dear members ,
>
>
>
> Since 1992 I work for Visio, an institution the helps visually impaired
> people. We have always been using the Teller Acuity Cards to determine
> the visual acuity in children.
>
> A new test has been presented on the scene, proposing to replace the
> Teller Acuity cards, because the TAC are expensive and sometime difficult
> to get. I enclose an example picture of the new cards.
>
>
>
> From my perspective and knowledge they have made some fundamental errors
>
> 1.       The test seems  ambiguous to me, because both object recognition
> part of our visual system as well as the much `lower" detection part of
our
> visual system is triggered by this stimulus
>
> 2.       The spatial frequency content of these stimuli (checkerboard
> patterns with a distinctive contour) is in the Fourier domain essentially
> different from the TAC bar patterns without a contour; nevertheless the
>  same cycl/cm are used.
>
> 3.       In addition to point 2: I think that the contour is a much
> stronger stimulus than the checkerboards.
>
>
>
> Could anybody reflect on this ?
>
>
>
> Most kindley,
>
>
>
>
>
> *drs. M.J. de Vries 69024716001*
>
>
>
> *Revalidatieoogarts*
>
> *Koninklijke Visio Noord-West Nederland Revalidatie & Advies*
>
> Hettenheuvelweg 41-43 1101 BM Amsterdam
>
> *T* 088 585 57 23/585 57 00   *M *0031 (0)6 50 51 86 13
>
>
>
> *Kinderoogarts-Ophthalmogenetica-Strabologie-Revalidatie*
>
> *Universitair Ziekenhuis Antwerpen  afdeling ophthalmologie*
>
> Wilrijkstraat 10
>
> 2650 Edegem
>
> *T* +32 3 821 30 00 *M* +31 6 50518613
>
>
>
>
>
>
>
> *------------------------------ DISCLAIMER. De informatie verzonden met
> dit e-mailbericht is uitsluitend bestemd voor de geadresseerde. Gebruik van
> deze informatie door anderen dan de geadresseerde is verboden.
> Openbaarmaking, vermenigvuldiging, verspreiding en/of verstrekking van deze
> informatie aan derden is niet toegestaan. Visio staat niet in voor de
> juiste en volledige overbrenging van de inhoud van een verzonden e-mail,
> noch voor tijdige ontvangst daarvan. ------------------------------*
> _______________________________________________
> visionlist mailing list
> visionlist at visionscience.com
> http://visionscience.com/mailman/listinfo/visionlist_visionscience.com
>